The Music app implements both flat and hierarchical navigation. At the top level, flat navigation enables switching between your library, your playlists, and radio. As you dive deeper, such as into the albums in your library, content is presented hierarchically.
Make it fast and easy to get to content. Structure information to require the least number of taps, swipes, and screens.
Restore the previous app state when the user returns to your app. Don't make someone retrace steps to reach their previous location in your app. Preserve and restore your app’s state so the user can continue where they left off. However, avoid resuming audio playback automatically unless it’s the primary feature of your app and is expected by the user.
In general, provide one path to each screen. People should always know where they are in your app and how to get to their next destination. Regardless of navigation style, it’s essential that the path through content is logical, predictable, and easy to follow.
When possible, use standard navigation components like tab bars and table views. Users are already familiar with these controls, and will intuitively know how to get around your app. Audio apps automatically adopt standard navigation controls. See Audio Apps.
Use a navigation bar to traverse a hierarchy of data. The navigation bar’s title can show the current position in the hierarchy, and the back button makes it easy to return to the previous location. For specific guidance, see Navigation Bars.
Use a tab bar to present peer categories of content or functionality. A tab bar lets people quickly and easily switch between categories, regardless of the current location. For specific guidance, see Tab Bars.